A new report on the state of patent litigation in the US shows that patent lawsuits appear to be more numerous—and more concentrated—than ever before.

The report by patent analysis firm Lex Machina shows that a big chunk of the 6,092 patent lawsuits filed last year came from a few entities. Unsurprisingly, the companies responsible for the most patent lawsuits are all "patent trolls," that is, entities with no business outside licensing and litigating patents. Terms for these companies seem to be proliferating, and Lex Machina uses one of the more diplomatic alternatives, calling them "patent monetization entities" or PMEs.

The number of lawsuits jumped 12.4 percent over 2012, which saw 5,418 new cases filed. That's the largest number of lawsuits ever filed in a year, but some of that rise is due to rule changes about how many defendants can be in a single lawsuit. Using another system of counting, which accounts for those rule changes, last year was the second-highest ever. The most litigious year overall remains 2011, when plaintiffs were rushing to file before the new America Invents Act rules took effect.

More Texas

The Eastern District of Texas has been a hotspot for patent cases for several years now. Originally a fast-moving "rocket docket," its time to trial has slowed to a crawl, yet it maintains its popularity. East Texas was the top filing spot for new patent lawsuits, with 1,495 filed there in 2013. Delaware, where many large corporations are headquartered, was second at 1,336. Central District of California, the nation's largest judicial district, trailed a distant third at 399 lawsuits.

Even within East Texas, the patent litigation landscape is highly concentrated. The district has seven federal judges, but 941 of the patent cases filed last year sit with a single judge, US District Judge Rodney Gilstrap. That's more than double the amount handled by the judge with the second-largest number of cases, US District Judge Leonard Stark of Delaware, who got 399 new cases last year.

Lex Machina

The judges who see the most cases are also, unsurprisingly, overseeing the largest number of merits decisions. Gilstrap oversaw 15 "merits decisions," which include any kind of case that weighs in on the quality of the patents, such as a jury trial or summary judgment decision. Two Delaware judges also each had 15 merits decisions. US District Judge Leonard Davis of East Texas handled 12 decisions.

East Texas' popularity is mainly due to the tendency of widely litigating trolls to file there. Last year, there were 97 different plaintiffs that filed five or more cases each in that district. Twenty-one plaintiffs filed 20 cases or more apiece.

"So much of patent litigation happens in a few districts, before relatively few judges," said Brian Howard, Lex Machina's legal data scientist, who spoke to Ars about the report.

More “trolls”

The high number of lawsuits is driven by patent troll suits. Lex Machina didn't measure what proportion of the lawsuits were due to "patent trolls," but other studies, using a conservative definition, have placed that figure at over 60 percent. However, Lex Machina did study other factors that show how the trolls are driving litigation.

Of the ten plaintiffs filing the most lawsuits, all are trolls. The most litigious troll last year was ArrivalStar, a company that Ars first reported on in 2012 when the company started suing public transit agencies. ArrivalStar, run by Vancouver resident Martin Jones, agreed to back away from that strategy after a US transit group lawyered up, but it continues to sue a vast array of private companies using different forms of vehicle-tracking technology.

Looking at the ten most frequently asserted patents, seven of them are from the ArrivalStar family of patents describing vehicle-tracking technology. Other patents on the most-asserted list include ones that originated at AT&T, Xerox, and Stanford University but are now in the hands of various trolls.

Patent trolling today is truly an industry—by one measure, it costs the economy $29 billion in direct legal costs each year. But while it drives a big chunk of litigation, it's not because of any giant eye-popping verdicts. Of the top ten patent damages awards last year, the biggest seven all went to disputes between competitors. The biggest verdict for a non-competitor was a case called Two-Way Media v. AT&T, which resulted in a $27.5 million verdict against AT&T.

While troll lawsuits proliferate, changes in case law have made it difficult for them to win huge verdicts. However, the Lex Machina statistics don't include cases where plaintiffs are attempting to win running royalties, such as Vringo's patent case against Google. In that case, Vringo has won a running royalty that could far outstrip the $30 million verdict it won in 2012.

The top targets for lawsuits were all tech companies. Apple was sued 59 times for patent infringement, while Amazon was sued 50 times. AT&T, Google, Dell, HTC, Samsung, Microsoft, LG, and HP rounded out the top-ten list, with those companies seeing at least 34 lawsuits each.